Abstract: In an electronic apparatus for measuring a difference of elevation between two points, said apparatus comprising: a tube made of a flexible material; a fluid with a low viscosity completely filling said tube; two piezoelectronical pressure transducers each connected to a source of electrical power and mounted at one extremity of the tube in contact with the fluid filling said tube to produce signal a proportional to the pressure of this fluid; electronic means connected to each of said piezoelectrical pressure transducers for processing the signals received from said transducers, said processing means comprising means for generating a signal proportional to the difference between the signals received from the transducers and means for converting said generated signal into a value indicating the difference of elevation between the extremities of the tube, and means for displaying said value indicating the difference of elevation, the improvement wherein it further comprises means for generating a signal propor

Abstract: An apparatus for measuring the deformation parameters of a periodic signal concealed in noise. The signal is transmitted by a transmitter controlled by a stable clock and received by a receiver also controlled by a stable clock of the same frequency as the one of the transmitter. The receiver comprises a detector for detecting the signal transmitted by the transmitter, means for resetting to a predetermined value the voltage detected by the detector at each integral number of cycles but at any particular time in the cycle, and an analog to digital converter connected to the detector for sampling the signal detected by the detector a predetermined number of times per cycle for converting the analog signal into a digital signal.